This invention relates to internal combustion engines and more particularly to improved apparatus for injecting water vapor and similar vapors in the form of low pressure steam into an internal combustion engine.
It has long been recognized that the effective octane rating for fuels for internal combustion engines may be increased by injecting water vapor, alcohol-water vapor and other vapors into the engine cylinders along with the air-fuel mixture. The injected vapors produce different effects including lowering combustion temperatures and thereby lowering the flame front propagation rate. This, in effect, is the same as an increase in the effective octane rating for the fuel. The lower combustion temperatures also improve the composition of the exhaust gases by reducing the formation of nitrous oxides and other pollutants. The retardant action on the flame front propagation rate also reduces or eliminates engine "knock" or "ping", thereby allowing either a higher engine compression ratio and/or a greater advance in the ignition timing. These changes, in turn, may provide a greater horse power output from the engine and/or a lower fuel consumption rate. Still another benefit received from vapor injection is a reduction in carbon deposits on the piston and cylinder walls. This in turn reduces engine wear and also reduces contamination of the engine lubricating oil.
Various methods have been used in the past for injecting water vapor and the like into the cylinders of internal combustion engines for controlling combustion. One early method merely involved passing intake air through an evaporator for moistening the air. Moistening may be accomplished by various techniques such as by passing the air through a porous member which is wetted with the liquid or by bubbling the air through a reservoir or tank holding the liquid. Moistened air has also been injected into the engine's intake manifold. However, with this method, the quantity of moisture added to the air is limited. Another prior art method involves spraying liquid directly either into a carburetor intake or into the intake manifold for the engine. With this method, it is difficult to provide a uniform air-fuel-water vapor mixture to all cylinders. There is also difficulty in uniformly atomizing the sprayed liquid to prevent large droplets of the liquid from entering at least some of the cylinders.